Why do I get "CUDA error: Out of memory", even on empty scenes?
retaking this now. I am using a NVIDIA GeForce GT 640M 512 MB (not the best, I know) in an iMac (21.5-inch, Late 2012) running OSX 10.11.5 (15F34) El Capitan. With CUDA version 7.5.27 and Blender 2.77a. I was struggling to render an empty image using GPU and CUDA. When I saw @cegaton suggestion: Reduce tile size. It made an empty image render with GPU. Maybe is the most we can do with it, but at least, we can get something. I was using X:64 and Y:64 tile size, and moved to X:32 and Y:32. If I find anything interesting, will post back. But maybe this is the limit. Hope it helps.